Earth Blog

Colorado, USA

November 2014

The atmosphere around a super-Earth exoplanet has been analysed for the first time by an international team of astronomers using ESO’s Very Large Telescope. The planet, which is known as GJ 1214b, was studied as it passed in front of its parent star and some of the starlight passed through the planet’s atmosphere. We now know that the atmosphere is either mostly water in the form of steam or is dominated by thick clouds or hazes. The results will appear in the 2 December 2010 issue of the journal Nature.

The planet GJ 1214b was confirmed in 2009 using the HARPS instrument on ESO’s 3.6-metre telescope in Chile. Initial findings suggested that this planet had an atmosphere, which has now been confirmed and studied in detail by an international team of astronomers, led by Jacob Bean (Harvard–Smithsonian Center for Astrophysics), using the FORS instrument on ESO’s Very Large Telescope.

“This is the first super-Earth to have its atmosphere analysed. We’ve reached a real milestone on the road toward characterising these worlds,” said Bean.

GJ 1214b has a radius of about 2.6 times that of the Earth and is about 6.5 times as massive, putting it squarely into the class of exoplanets known as super-Earths. Its host star lies about 40 light-years from Earth in the constellation of Ophiuchus (the Serpent Bearer). It is a faint star, but it is also small, which means that the size of the planet is large compared to the stellar disc, making it relatively easy to study. The planet travels across the disc of its parent star once every 38 hours as it orbits at a distance of only two million kilometres: about seventy times closer than the Earth orbits the Sun.

To study the atmosphere, the team observed the light coming from the star as the planet passed in front of it. During these transits, some of the starlight passes through the planet’s atmosphere and, depending on the chemical composition and weather on the planet, specific wavelengths of light are absorbed. The team then compared these precise new measurements with what they would expect to see for several possible atmospheric compositions.

Before the new observations, astronomers had suggested three possible atmospheres for GJ 1214b. The first was the intriguing possibility that the planet was shrouded by water, which, given the close proximity to the star, would be in the form of steam. The second possibility was that this is a rocky world with an atmosphere consisting mostly of hydrogen, but with high clouds or hazes obscuring the view. The third option was that this exoplanet was like a mini-Neptune, with a small rocky core and a deep hydrogen-rich atmosphere.

The new measurements do not show the telltale signs of hydrogen and hence rule out the third option. Therefore, the atmosphere is either rich in steam, or it is blanketed by clouds or hazes, similar to those seen in the atmospheres of Venus and Titan in our Solar System, which hide the signature of hydrogen..

“Although we can’t yet say exactly what that atmosphere is made of, it is an exciting step forward to be able to narrow down the options for such a distant world to either steamy or hazy,” says Bean. “Follow-up observations in longer wavelength infrared light are now needed to determine which of these atmospheres exists on GJ 1214b.”

Ceres' Haulani Crater, with a diameter of 21 miles (34 kilometers), shows evidence of landslides from its crater rim. Smooth material and a central ridge stand out on its floor. This image was made using data from NASA's Dawn spacecraft when it was in its high-altitude mapping orbit, at a distance of 915 miles (1,470 kilometers) from Ceres.

This enhanced color view allows scientists to gain insight into materials and how they relate to surface morphology. Rays of bluish ejected material are prominent in this image. The color blue in such views has been associated with young features on Ceres.

Alaska, USA

March 18, 2015

This image captures the stunning NGC 6535, a globular cluster 22 000 light-years away in the constellation of Serpens (The Serpent) that measures one light-year across.

Globular clusters are tightly bound groups of stars which orbit galaxies. The large mass in the rich stellar centre of the globular cluster pulls the stars inward to form a ball of stars. The word globulus, from which these clusters take their name, is Latin for small sphere.

Globular clusters are generally very ancient objects formed around the same time as their host galaxy. To date, no new star formations have been observed within a globular cluster, which explains the abundance of aging yellow stars in this image, most of them containing very few heavy elements.

NGC 6535 was first discovered in 1852 by English astronomer John Russell Hind. The cluster would have appeared to Hind as a small, faint smudge through his telescope. Now, over 160 years later, instruments like the Advanced Camera for Surveys (ACS) and Wide Field Camera 3 (WFC3) on the NASA/ESA Hubble Space Telescope allow us to capture the cluster close up and marvel at its contents in detail.

Dozens of newborn stars sprouting jets from their dusty cocoons have been spotted in images from NASA's Spitzer Space Telescope. In this view showing a portion of sky near Canis Major, infrared data from Spitzer are green and blue, while longer-wavelength infrared light from NASA's Wide-field Infrared Survey Explorer (WISE) are red.

The jets appear in green, while young stars are a yellow-orange hue. Some of the jets can be seen as streaks, while others appear as blobs because only portions of the jet can be seen. In some cases, the stars producing jets can't be seen while their jets can. Those stars are so embedded in their dusty cocoon that they are too faint to be seen at Spitzer's wavelengths.

This is a lesser-known region of star formation, located near the outer edge of our Milky Way galaxy. Spitzer is showing that even these more sparse regions of the galaxy are aglow with stellar youth.

The pink hues are from organic star-forming molecules called polycyclic aromatic hydrocarbons. Stars in the pink regions are a bit older than the rambunctious ones spewing jets, but still relatively young in cosmic terms.

In this image, Spitzer's 3.6- and 4.5-micron data are blue and green, respectively, while WISE's 12-micron data are red. The Spitzer data were taken as part of the mission's Galactic Legacy Infrared Mid-Plane Survey Extraordinaire 360, or Glimpse 360 project, which is pointing the Spitzer Space telescope away from the galactic center to complete a full 360-degree scan of the Milky Way plane.

WISE all-sky observations are boosting Spitzer's imaging capabilities by providing the longer-wavelength infrared coverage the mission lost when it ran out of coolant, as planned, in 2009.

This nighttime photo of Florida was taken from the International Space Station by Expedition 51 Flight Engineer Thomas Pesquet of the European Space Agency, in March 2017. Bright lights of cities stand out, including the Miami-Fort Lauderdale metropolitan area, the Tampa Bay region along the Gulf Coast, and in the middle, Orlando.

Visible on Florida's Atlantic coast is the Cape Canaveral area where, currently, launch preparations are underway at NASA's Kennedy Space Center for the eleventh SpaceX cargo resupply mission to the International Space Station, targeted for liftoff at 5:55 p.m. EDT on Thursday, June 1, from Launch Complex 39A.

A solar prominence at the sun's edge put on quite a display of plasma being pushed and pulled by unstable magnetic fields (May 22-24, 2017). We call them hedgerow prominences because they look somewhat like a hedge of bushes. This is one of the better examples of this type of solar phenomenon than any we have seen in quite some time.

The NASA/ESA Hubble Space Telescope is famous for its jaw-dropping snapshots of the cosmos. At first glance this picture appears to be quite the opposite, showing just a blur of jagged spikes, speckled noise, and weird, clashing colours — but once you know what you are looking at, images like this one are no less breathtaking.

This shows a distant galaxy — visible as the smudge to the lower right — as it begins to align with and pass behind a star sitting nearer to us within the Milky Way. This is an event known as a transit. The star is called HD 107146, and it sits at the centre of the frame. Its light has been blocked in this image to make its immediate surroundings and the faint galaxy visible — the position of the star is marked with a green circle.

The concentric orange circle surrounding HD 107146 is a circumstellar disc — a disc of debris orbiting the star. In the case of HD 107146 we see the disc face-on. As this star very much resembles our Sun, it is an interesting scientific target to study: its circumstellar disc could be analogous to the asteroids in our Solar System and the Kuiper belt.

A detailed study of this system is possible because of the much more distant galaxy — nicknamed the “Vermin Galaxy” by some to reflect their annoyance at its presence — as the star passes in front of it. The unusual pairing was first observed in 2004 by Hubble’s Advanced Camera for Surveys, and again in 2011 by Hubble’s Space Telescope Imaging Spectrograph. The latter image is shown here, as the Vermin Galaxy began its transit behind HD 107146. The galaxy will not be fully obscured until around 2020, but interesting science can be done even while the galaxy is only partly obscured. Light from the galaxy will pass through the star’s debris discs before reaching our telescopes, allowing us to study the properties of the light and how it changes, and thus infer the characteristics of the disc itself.

Russell, Kansas, USA

May 25, 2012

This photograph shows the last face on view of the Great Dark Spot that Voyager will make with the narrow angle camera. The image was shuttered 45 hours before closest approach at a distance of 2.8 million kilometers (1.7 million miles). The smallest structures that can be seen are of an order of 50 kilometers (31 miles). The image shows feathery white clouds that overlie the boundary of the dark and light blue regions. The pinwheel (spiral) structure of both the dark boundary and the white cirrus suggest a storm system rotating counterclockwise. Periodic small scale patterns in the white cloud, possibly waves, are short lived and do not persist from one Neptunian rotation to the next. This color composite was made from the clear and green filters of the narrow-angle camera.

The Big Bang theory is the prevailing cosmological model for the universe from the earliest known periods through its subsequent large-scale evolution. The model describes how the universe expanded from a very high density and high temperature state, and offers a comprehensive explanation for a broad range of phenomena, including the abundance of light elements, the cosmic microwave background, large scale structure and Hubble's Law. If the known laws of physics are extrapolated to the highest density regime, the result is a singularity which is typically associated with the Big Bang. Detailed measurements of the expansion rate of the universe place this moment at approximately 13.8 billion years ago, which is thus considered the age of the universe. After the initial expansion, the universe cooled sufficiently to allow the formation of subatomic particles, and later simple atoms. Giant clouds of these primordial elements later coalesced through gravity in halos of dark matter, eventually forming the stars and galaxies visible today.

Since Georges Lemaître first noted in 1927 that an expanding universe could be traced back in time to an originating single point, scientists have built on his idea of cosmic expansion. While the scientific community was once divided between supporters of two different expanding universe theories, the Big Bang and the Steady State theory, empirical evidence provides strong support for the former. In 1929, from analysis of galactic redshifts, Edwin Hubble concluded, that galaxies are drifting apart; this is important observational evidence consistent with the hypothesis of an expanding universe. In 1964, the cosmic microwave background radiation was discovered, which was crucial evidence in favor of the Big Bang model, since that theory predicted the existence of background radiation throughout the universe before it was discovered. More recently, measurements of the redshifts of supernovae indicate that the expansion of the universe is accelerating, an observation attributed to dark energy's existence. The known physical laws of nature can be used to calculate the characteristics of the universe in detail back in time to an initial state of extreme density and temperature.

Childress, Texas, USA

This image of the Egg Nebula, also known as CRL2688 and located roughly 3, 000 light-years from us, was taken in red light with the Wide Field and Planetary Camera 2 (WFPC2) aboard the Hubble Space Telescope.

This image sheds new light on the poorly understood ejection of stellar matter which accompanies the slow death of Sun-like stars.

This is a NASA/ESA Hubble Space Telescope image of the galaxy cluster Abell 370. Shown in blue on the image is a map of the dark matter found within the cluster. This cluster was part of a study of 72 galaxy cluster collisions which determined that dark matter interacts with other dark matter even less than previously thought.

Broken Bow, Nebraska, USA

May 25, 2013

Named for its resemblance to a coiling spiral seen face on, the Helix Nebula (NGC 7293) is a challenging stargazing target that has a more complex three-dimensional structure than expected. Now, the nebula has a new portrait, created by the penetrating infrared gaze of NASA's Spitzer Space Telescope, which was released at the 207th meeting of the American Astronomical Society on Jan. 9, 2006.

The nebula, which is composed of gaseous shells and disks puffed out by a dying sunlike star, exhibits complex structure on even the smallest visible scales.

This image is a composite of infrared data from Spitzer and visible-light data from NASA's Hubble Space Telescope.

Using a quartet of space observatories, University of Maryland astronomers may have cracked a 45-year mystery surrounding two ghostly spiral arms in the galaxy M106.

The Maryland team, led by Yuxuan Yang, took advantage of the unique capabilities of NASA's Chandra X-ray Observatory, NASA's Spitzer Space Telescope, the European Space Agency's XMM-Newton X-ray observatory, and data obtained almost a decade ago with NASA's Hubble Space Telescope.

M106 (also known as NGC 4258) is a stately spiral galaxy 23.5 million light-years away in the constellation Canes Venatici. In visible-light images, two prominent arms emanate from the bright nucleus and spiral outward. These arms are dominated by young, bright stars, which light up the gas within the arms. "But in radio and X-ray images, two additional spiral arms dominate the picture, appearing as ghostly apparitions between the main arms," says team member Andrew Wilson of the University of Maryland. These so-called "anomalous arms" consist mostly of gas.

"The nature of these anomalous arms is a long-standing puzzle in astronomy," says Yang. "They have been a mystery since they were first discovered in the early 1960s."

By analyzing data from XMM-Newton, Spitzer, and Chandra, Yang, Bo Li, Wilson, and Christopher Reynolds, all at the University of Maryland at College Park, have confirmed earlier suspicions that the ghostly arms represent regions of gas that are being violently heated by shock waves.

Previously, some astronomers had suggested that the anomalous arms are jets of particles being ejected by a supermassive black hole in M106's nucleus. But radio observations by the National Radio Astronomy Observatory's Very Long Baseline Array, and the Very Large Array in New Mexico, later identified another pair of jets originating in the core. "It is highly unlikely that an active galactic nucleus could have more than one pair of jets," says Yang.

In 2001, Wilson, Yang, and Gerald Cecil, of the University of North Carolina, Chapel Hill, noted that the two jets are tipped 30 degrees with respect to the galaxy disk. But if one could vertically project the jets onto the disk, they would line up almost perfectly with the anomalous arms. Figuring that this alignment was not strictly a matter of chance, Wilson, Yang, and Cecil proposed that the jets heat the gas in their line of travel, forming an expanding cocoon. Because the jets lie close to M106's disk, the cocoon heats gas in the disk and generates shock waves, heating the gas to millions of degrees and causing it to radiate brightly in X-rays and other wavelengths.

To test this idea, Yang and his colleagues looked at archival spectral observations from XMM-Newton. With XMM-Newton's superb sensitivity, the team could measure the gas temperature in the anomalous arms and also see how strongly X-rays from the gas are absorbed en route by intervening material.

"One of the predictions of this scenario is that the anomalous arms will gradually be pushed out of the galactic disk plane by jet-heated gas," says Yang. The XMM-Newton spectra show that X-rays are more strongly absorbed in the direction of the northwest arm than in the southeast arm. The results strongly suggest that the southeast arm is partly on the near side of M106's disk, and the northwest arm is partly on the far side.

The scientists noted that these observations show clear consistency with their scenario. Confirmation of this interpretation has recently come from archival observations from NASA's Spitzer Space Telescope, whose infrared view shows clear signs that X-ray emission from the northwest arm is being absorbed by warm gas and dust in the galaxy's disk. Moreover, Chandra's superior imaging resolution gives clear indications of gas shocked by interactions with the two jets.

Besides addressing the mystery of the anomalous arms, these observations allowed the team to estimate the energy in the jets and gauge their relationship to M106's central black hole.

Alaska, USA

Astronomers have discovered the second super-Earth exoplanet for which they have determined the mass and radius, giving vital clues about its structure. It is also the first super-Earth where an atmosphere has been found. The exoplanet, orbiting a small star only 40 light-years away from us, opens up dramatic new perspectives in the quest for habitable worlds. The planet, GJ1214b, has a mass about six times that of Earth and its interior is likely to be mostly made of water ice. Its surface appears to be fairly hot and the planet is surrounded by a thick atmosphere, which makes it inhospitable for life as we know it on Earth.

In this week’s issue of Nature, astronomers announce the discovery of a planet around the nearby, low-mass star GJ1214. It is the second time a transiting super-Earth has been detected, after the recent discovery of the planet Corot-7b. A transit occurs when the planet's orbit is aligned so that we see it crossing the face of its parent star. The newly discovered planet has a mass about six times that of our terrestrial home and 2.7 times its radius, falling in size between the Earth and the ice giants of the Solar System, Uranus and Neptune.

Although the mass of GJ1214b is similar to that of Corot-7b, its radius is much larger, suggesting that the composition of the two planets must be quite different. While Corot-7b probably has a rocky core and may be covered with lava, astronomers believe that three quarters of GJ1214b is composed of water ice, the rest being made of silicon and iron.

GJ1214b orbits its star once every 38 hours at a distance of only two million kilometres — 70 times closer to its star than the Earth is to the Sun. “Being so close to its host star, the planet must have a surface temperature of about 200 degrees Celsius, too hot for water to be liquid,” says David Charbonneau, lead author of the paper reporting the discovery.

When the astronomers compared the measured radius of GJ1214b with theoretical models of planets, they found that the observed radius exceeds the models’ predictions: there is something more than the planet’s solid surface blocking the star’s light — a surrounding atmosphere, 200 km thick. “This atmosphere is much thicker than that of the Earth, so the high pressure and absence of light would rule out life as we know it,” says Charbonneau, “but these conditions are still very interesting, as they could allow for some complex chemistry to take place.”

“Because the planet is too hot to have kept an atmosphere for long, GJ1214b represents the first opportunity to study a newly formed atmosphere enshrouding a world orbiting another star,” adds team member Xavier Bonfils. “Because the planet is so close to us, it will be possible to study its atmosphere even with current facilities.”

The planet was first discovered as a transiting object within the MEarth project, which follows about 2000 low-mass stars to look for transits by exoplanets. To confirm the planetary nature of GJ1214b and to obtain its mass (using the so-called Doppler method), the astronomers needed the full precision of the HARPS spectrograph, attached to ESO’s 3.6-metre telescope at La Silla. An instrument with unrivalled stability and great precision, HARPS is the world’s most successful hunter for small exoplanets.

“This is the second super-Earth exoplanet for which the mass and radius could be obtained, allowing us to determine the density and to infer the inner structure,” adds co-author Stephane Udry. “In both cases, data from HARPS was essential to characterise the planet.”

“The differences in composition between these two planets are relevant to the quest for habitable worlds,” concludes Charbonneau. If super-Earth planets in general are surrounded by an atmosphere similar to that of GJ1214b, they may well be inhospitable to the development of life as we know it on our own planet.

NASA's Cassini spacecraft captured this view as it neared icy Enceladus for its closest-ever dive past the moon's active south polar region. The view shows heavily cratered northern latitudes at top, transitioning to fractured, wrinkled terrain in the middle and southern latitudes. The wavy boundary of the moon's active south polar region -- Cassini's destination for this flyby -- is visible at bottom, where it disappears into wintry darkness.

This view looks towards the Saturn-facing side of Enceladus. North on Enceladus is up and rotated 23 degrees to the right. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on October 28, 2015.

The view was acquired at a distance of approximately 60,000 miles (96,000 kilometers) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 45 degrees. Image scale is 1,896 feet (578 meters) per pixel.